This invention relates to a novel process to remove a portion of acid gas from a sulfur compound stream to produce a low acid gas sulfur product. More specifically, this invention relates to a novel process to remove a portion of acid gas from the sulfur compound stream by adsorption on an adsorption media followed by regeneration of the adsorption media when the adsorption capacity has been reached.
Generally, when a sulfur compound stream such as dimethylsulfide (DMS) or methyl mercaptan, is produced, it can contain carbon disulfide (CS2) in the range of 0 to about 0.5 wt %. Various methods for removing CS2 from DMS and mercaptans are known in the art. Treatment with aqueous caustic for CS2 removal is a possible route for producing a low CS2 DMS. In this process, aqueous caustic is added to the sulfur compound stream in a tank to form a mixture. The mixture is circulated through a roll pump. Subsequently, the mixing is stopped and two phases, an aqueous phase and a an organic phase are formed. The two phases are allowed to separate, and the aqueous phase is drained off the bottom of the tank.
However in this process, it is necessary to add a phase transfer agent such as methanol or trimethyl amine, in order to provide adequate contact between the aqueous phase and the organic phase. Subsequent draining of the aqueous caustic can cause a high total organic carbon (TOC) count at plant wastewater systems if this route is employed. There is a need for an efficient, environmental-friendly process to remove acid gas from a sulfur compound stream.
Alternatively, the acid gas can be removed via distillation. However, CS2 and DMS form an azeotrope that limits the ultimate purity of DMS that can be obtained via distillation.
Other markets for high purity DMS (low CS2) may become available in the future. Dimethyl sulfoxide (DMSO), which is produced via partial oxidation of high purity DMS, is one possibility. Another market opportunity is low CS2 DMS for ethylene furnace treatment. High CS2 content in the DMS for treatment of the cracking furnace tubes can result in off specification C5+ streams which in turn cause a number of unfavorable consequences in downstream processes. The inventors provide such a process in this patent application.
A novel method to remove acid gas from a sulfur compound stream is disclosed. The acid gas consists of at least one compound selected from the group consisting of carbon disulfide (CS2), carbonyl sulfide (COS), carbon dioxide (CO2), or hydrogen sulfide (H2S). The sulfur compound stream is selected from a group consisting of sulfides, disulfides, or thiols (mercaptans). Preferably, the S compound stream is selected from one or more of the following: DMS, diethylsulfide (DES), dimethyldisulfide (DMDS), methyl ethyl sulfide (MES), methyl isopropyl sulfide, methyl mercaptan, or ethyl mercaptan. Specifically, the method relates to a novel process to remove CS2 from a sulfur containing stream by adsorption on an adsorption media comprising an activated alumina adsorbent followed by regeneration of the activated alumina after adsorption capacity has been reached. The adsorption media comprises an activated alumina, which has been previously treated with one or more alkali metal compounds, one or more alkaline earth metal compounds, or a mixture thereof; then regenerating the adsorbent after the adsorption capacity has been reached. Specifically, the adsorption media comprises an activated alumina, which has been previously treated with caustic; then regenerating the adsorbent after the adsorption capacity has been reached. Preferably, the caustic used in the treatment of the activated alumina is sodium hydroxide (NaOH). The activated alumina will adsorb acid gases (CO2, COS, H2S and CS2) from liquid hydrocarbon streams. The process to adsorb acid gas with activated alumina from a liquid hydrocarbon stream is disclosed in U.S. Pat. Nos. 4,835,338 and 4,493,715 herein incorporated by reference. However, using the alumina impregnated with caustic or other adsorbent medias to remove acid gas from a sulfur containing stream would not be readily apparent by one skilled in the art. One skilled in the art may believe that cleaving of sulfur compounds in the sulfur compound stream could occur thus making the ability of the adsorbent to remove acid gas ineffective. However, a new use and a process have been developed to use activated alumina to remove acid gas from the sulfur compound stream.
An object of this invention is to remove a portion of acid gas from a sulfur compound stream to produce a low acid gas sulfur product.
Another object of this invention is to remove a portion of the acid gas from a wet sulfur compound stream to produce a low acid gas sulfur product.
Another object of this invention is to provide a process for the removal of a portion of CS2 from a sulfur compound stream by adsorption on an adsorption media comprising an activated alumina adsorbent followed by regeneration of the activated alumina after the adsorption capacity has been reached.
Another object of this invention is to provide an improved process for removal of a portion of CS2 from a sulfur compound stream by adsorption on a an adsorption media comprising an activated alumina which has been previously treated with one or more alkali metal compounds, alkaline earth metal compounds, or a mixture thereof, and then regenerating the adsorbent after the adsorption capacity has been reached.
Another object of this invention is to provide an improved process for removal of a portion of CS2 from a sulfur compound stream by adsorption on a adsorption media comprising an activated alumina which has been previously treated with caustic.
Another object of this invention is to provide a process to remove CS2 from a DMS stream by adsorption on a an adsorption media comprising adsorbing said CS2 in an adsorption zone to remove a portion of said CS2 from said DMS stream to produce a low CS2 DMS product wherein said adsorption zone comprises an adsorber containing activated alumina adsorbent; wherein said activated alumina has been previously treated with one or more alkali metal compounds, one or more alkaline earth metal compounds, or a mixture thereof.
Another object of this invention is to provide a process to remove CS2 from a DMS stream by adsorption on a an adsorption media comprising adsorbing said CS2 in an adsorption zone to remove a portion of said CS2 from said DMS stream to produce a low CS2 DMS product wherein said adsorption zone comprises an adsorber containing activated alumina adsorbent; wherein said activated alumina has been treated with caustic.
Another object of this invention is to provide a process to remove CS2 from a DMS stream by adsorption on a an adsorption media comprising adsorbing said CS2 in an adsorption zone to remove a portion of said CS2 from said DMS to produce a low CS2 DMS product wherein said adsorption zone comprises an adsorber containing activated alumina adsorbent; wherein said activated alumina has been previously treated with one or more alkali metal compounds, one or more alkaline earth metal compounds, or a mixture thereof, wherein said adsorber is operated at a temperature in a range of xe2x88x9225xc2x0 C. to about 100xc2x0 C.; wherein said adsorber is operated to its adsorption capacity and regenerated with nitrogen or natural gas at a temperature in a range of 235xc2x0 C. to 300xc2x0 C.
Another object of this invention is to provide a process to remove CS2 from a DMS stream by adsorption on a an adsorption media comprising adsorbing said CS2 in an adsorption zone to remove a portion of said CS2from said DMS to produce a low CS2 DMS product wherein said adsorption zone comprises an adsorber containing activated alumina adsorbent; wherein said activated alumina has been treated with caustic; wherein said adsorber is operated at a temperature in a range of xe2x88x9225xc2x0 C. to about 100xc2x0 C.; wherein said adsorber is operated to its adsorption capacity and regenerated with nitrogen or natural gas at a temperature in a range of 235xc2x0 C. to 300xc2x0 C. In accordance with one embodiment of this invention, a process to remove acid gas from a sulfur containing stream, said process comprising (or optionally, xe2x80x9cconsisting essentially ofxe2x80x9d or xe2x80x9cconsisting ofxe2x80x9d) the following step:
adsorbing said acid gas in an adsorption zone to remove a portion of said acid gas from said sulfur compound stream to produce a low acid gas sulfur product.
In accordance with another embodiment of this invention, a process to remove acid gas from a sulfur containing stream, said process comprising (or optionally, xe2x80x9cconsisting essentially ofxe2x80x9d or xe2x80x9cconsisting ofxe2x80x9d) the following step:
adsorbing said CS2 in an adsorption zone to remove a portion of CS2 from said sulfur compound stream to produce a low CS2 sulfur product.
In accordance with another embodiment of this invention, a process to remove acid gas from a sulfur containing stream, said process comprising (or optionally, xe2x80x9cconsisting essentially ofxe2x80x9d or xe2x80x9cconsisting ofxe2x80x9d) the following step:
adsorbing said CS2 in an adsorption zone to remove a portion of said CS2 from said DMS to produce a low CS2 DMS product wherein said adsorption zone comprises an adsorber containing activated alumina adsorbent; wherein said activated alumina has been previously treated with one or more alkali metal compounds, one or more alkaline earth metal compounds, or a mixture thereof.
In accordance with another embodiment of this invention, a process to remove acid gas from a sulfur containing stream, said process comprising (or optionally, xe2x80x9cconsisting essentially ofxe2x80x9d or xe2x80x9cconsisting ofxe2x80x9d) the following step:
adsorbing said CS2 in an adsorption zone to remove a portion of said CS2 from said DMS to produce a low CS2 DMS product wherein said adsorption zone comprises an adsorber containing activated alumina adsorbent; wherein said activated alumina has been treated with caustic.
In accordance with another embodiment of this invention, a process to remove acid gases from a sulfur containing stream, said process comprising (or optionally, xe2x80x9cconsisting essentially ofxe2x80x9d or xe2x80x9cconsisting ofxe2x80x9d) the following step:
adsorbing said CS2 in an adsorption zone to remove a portion of said CS2 from said DMS to produce a low CS2 DMS product wherein said adsorption zone comprises an adsorber containing activated alumina adsorbent; wherein said activated alumina has been previously treated with one or more alkali metal compounds, one or more alkaline earth metal compounds, or a mixture thereof; wherein said adsorber is operated at a temperature in a range of xe2x88x9225xc2x0 C. to about 100xc2x0 C.; wherein said adsorber is operated to its adsorption capacity and regenerated with nitrogen or natural gas at a temperature in a range of 235xc2x0 C. to 300xc2x0 C.
In accordance with another embodiment of this invention, a process to remove acid gases from a sulfur containing stream, said process comprising (or optionally, xe2x80x9cconsisting essentially ofxe2x80x9d or xe2x80x9cconsisting ofxe2x80x9d) the following step:
adsorbing said CS2 in an adsorption zone to remove a portion of said CS2 from said DMS to produce a low CS2 DMS product wherein said adsorption zone comprises an adsorber containing activated alumina adsorbent; wherein said activated alumina has been treated with caustic; wherein said adsorber is operated at a temperature in a range of xe2x88x9225xc2x0 C. to about 100xc2x0 C.; wherein said adsorber is operated to its adsorption capacity and regenerated with nitrogen or natural gas at a temperature in a range of 235xc2x0 C. to 300xc2x0 C.
These objects, and other objects, will become more apparent to others with ordinary skill in the art after reading this disclosure.
In a first embodiment of this invention, a process to remove carbon disulfide from a sulfur containing stream is provided. The process comprises the following steps:
Step (1) is adsorbing said acid gas in an adsorption zone to remove a portion of the acid gas from the sulfur compound stream to produce a low acid gas sulfur product.
The acid gas is at least one compound selected from the group consisting of hydrogen sulfide (H2S), carbon dioxide (CO2), carbonyl sulfide (COS), and carbon disulfide (CS2). Preferably the acid gas is CS2.
The sulfur containing stream is at least one selected from a group consisting of sulfides, disulfides, and thiols (mercaptans) or mixtures thereof. Preferably, the sulfur containing stream is at least one selected from the group consisting of DMS, DMDS, MES, methyl isopropyl sulfide, methyl mercaptan, and ethyl mercaptan. The mercaptan compounds have a chemical formula of Rxe2x80x94Sxe2x80x94H, wherein R is a hydrocarbon radical having 1 to 12 carbons. Generally, the acid gas in the sulfur compound stream is less than about 5 wt %. Preferably, the acid gas in the sulfur compound stream is less than 1 wt %. Most preferably, the acid gas in the sulfur compound stream is less than 2000 ppmw. The amount of CS2 in the sulfur compound stream is less than about 5 wt %. Preferably, the CS2 is less than 1 wt %. Most preferably, the CS2 in the sulfur compound stream is less than 2000 ppmw.
Acid gas is adsorbed from the sulfur compound stream in an adsorption zone. The adsorbing can be conducted in the adsorption zone by any means known in the art. Preferably the adsorption zone comprises an adsorber having an adsorption media. The adsorption media is selected from a group consisting of activated alumina, silicas, zinc oxides or alkali metal compounds. Generally, the activated alumina comprises an activated alumina, which has been previously treated with one or more alkali metal compounds, one or more alkaline earth metal compounds, or a mixture thereof. Specifically, the activated alumina can be previously impregnated with a caustic compound such as, for example sodium hydroxide. The silicas are comprised of, silicon, oxygen and at least one metal.
The pressure in the adsorber is in the range of 0 psig to about 1000 psig. Preferably, the pressure is in a range of 10 psig to 200 psig. Most preferably, the pressure is in a range of 25 psig to 60 psig. The temperature in the adsorber is in a range of about xe2x88x9225xc2x0 C. to about 100xc2x0 C. Preferably, the temperature is in a range of 0xc2x0 C. to about 50xc2x0 C. Most preferably, the temperature is in a range of 10xc2x0 C. to 25xc2x0 C.
The acid as in the low acid gas sulfur product is less than about 2.5 wt %. Preferably, the acid gas in the low gas sulfur product is less than about 1wt %. Most preferably, the acid gas in the low acid gas sulfur product is less than 500 ppmw. When removing CS2 from a sulfur compound stream, the amount of CS2 in the in low acid gas sulfur product is less than about 2.5 wt %. Preferably, the CS2 in the low gas sulfur product is less than about 1 wt %. More preferably, the CS2 in the low acid gas sulfur product is less than 500 ppmw.
When removing CS2 from a DMS stream to form low CS2 DMS, the amount of CS2 in the low CS2 DMS is less than about 2.5 wt %. Preferably, the CS2 in the low CS2 DMS is less than 1 wt %. Most preferably, the CS2 in the low DMS product is less than 500 ppmw.
Step (2) is optionally drying the wet sulfur containing stream in a drying zone to produce the sulfur containing stream. The water content of the sulfur containing stream is sufficiently dry to prevent downstream operational problems. Generally, the water content is in the range of less than 2500 ppmw. Preferably, the water content of the sulfur containing stream is less than 100 ppmw. Most preferably, the water content of the sulfur containing stream is less than 10 ppmw. Drying in the drying zone can be accomplished by any means known in the art. For example, molecular sieve beds can be utilized to remove water. Preferably, molecular sieve beds are Type 3A.
Step (3) is optionally regenerating the adsorbent media in the adsorption zone when adsorption capacity of the adsorbent media has been reached.
The regeneration process comprises passing a regeneration gas through the adsorbent media to produce an acid gas rich stream. A regeneration gas can be any gas known in the art to remove acid gas from the adsorbent media. Preferably, the regeneration gas is selected from the group consisting of natural gas and nitrogen. The composition of the regeneration gas has an acid gas concentration of less than about 0.5 vol %. Preferably, the composition of the regeneration gas has an acid gas concentration of less than about 0.1 vol %. Most preferably, the composition of the regeneration gas has acid gas concentration of less than about 0.05 vol %.
Generally, the temperature of the regeneration gas is in a range of about 220xc2x0 C. to about 350xc2x0 C. Preferably, the temperature of the regeneration gas is in a range of about 245xc2x0 C. to about 275xc2x0 C. Most preferably, the temperature of the regeneration gas is in a range of 245xc2x0 C. to 255xc2x0 C.
The pressure of the regeneration gas is in a range of 0 psig to about 1000 psig. Preferably, the regeneration gas pressure is in a range of about 5 psig to about 50 psig. Most preferably, the pressure is in the range of 5 psig to 20 psig.